1. Field of the Invention
The present invention generally relates to electrophotographic image forming apparatuses, and particularly to an image forming apparatus such as a copying machine, a printer, or a facsimile machine.
2. Description of the Related Art
In order to reduce sizes of apparatuses and to improve operability, as a type of process cartridge in which a photosensitive drum, a charger, a developing device, etc. are integrated, an image forming apparatus in which an optical path for an image-exposure light from an exposing device to the photosensitive drum is provided in a substantially horizontal direction, and in which a fixing device is disposed above the photosensitive drum, has been proposed.
In the conventional image forming apparatus, the developing device for attaching a toner to an electrostatic latent image formed on the photosensitive drum to form a visible toner image is urged toward the photosensitive drum by an urging member so that a developing sleeve of the developing device is abutted on the photosensitive drum.
In the conventional image forming apparatus employing the process-cartridge arrangement described above, in which the optical path for the image-exposure light from the exposing device to the photosensitive drum is disposed horizontally, it has been difficult to allow a large amount of toner to be contained in a developer container in the developing device since a space for the optical path for image exposure is provided between the charger and the developing device in the process cartridge.
U.S. Pat. No. 5,839,032 discloses an arrangement in which a path for transporting a recording medium is provided in a direction extending from a lower position to an upper position and in which a developing device is disposed below a laser exposing device while a toner supplying container is disposed above the laser exposing device. In the image forming apparatus, two mirrors are used so that a laser beam from a polygon mirror in the laser exposing device will be incident diagonally on a photoreceptor.
However, in the image forming apparatus disclosed in U.S. Pat. No. 5,839,032, the two mirrors for reflecting the laser beam from the polygon mirror are needed in the laser exposing device. Thus, the number of parts constituting the laser exposing device is large and the cost is high. Furthermore, since the arrangement is such that the light from the laser exposing device is incident diagonally on the photoreceptor, a part of the case of the laser exposing device projects upward, increasing the size of the laser exposing device in the vertical direction. This has been a factor that inhibits reduction in the sizes of image forming apparatuses.